This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | -1 |
| 3 | 14 |
| 4 | 9 |
| 5 | -1516 |
| 6 | 4345 |
| 7 | 507870 |
| 8 | -4984063 |
| 9 | -367545880 |
| 10 | 7749976401 |
| 11 | 471799390490 |
| 12 | -18036953224367 |
| 13 | -948817553760324 |
| 14 | 60774529797257081 |
| 15 | 2736041193224490494 |
| 16 | -284790488755979731455 |
| 17 | -10493764378757426300848 |
| 18 | 1792499910367109444364961 |
| 19 | 49177040508763120698604578 |